我正在尝试使用pip安装软件包。皮普告诉我它已经过时了，我应该更新它。当我尝试更新pip时，它告诉我我已经更新了，并且有pip的新版本可用，我应该使用我刚才用来更新它的命令。
➜ ~ pip install --upgrade pip
Requirement already up-to-date: pip in /opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages
You are using pip version 7.0.3, however version 7.1.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
有什么问题？如何更新pip并打破循环？
系统信息：
➜ ~ which python
/opt/local/bin/python
➜ ~ python --version
Python 3.4.3
➜ ~ which pip
/opt/local/Library/Frameworks/Python.framework/Versions/3.4/bin/pip
➜ ~ pip --version
pip 7.1.2 from /opt/local/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/site-packages (python 3.4)